The present invention relates to fluid filters, and more particularly, a fluid filter having a pressure relief valve.
U.S. Reissued Pat. No. 37,165, assigned to Davco Technology, L.L.C., discloses a diesel fuel processor of the type generally shown in FIG. 1. That filter provides the user with a practical estimate of the condition of the filter element 20 as a function of the height of the fluid level in the upper filter chamber 17 as the fluid seeks the least possible pressure differential across the filter element 20. During operation of the engine, fuel moves from the lower chamber 16, through passage 15 to upper chamber 17, through the cylindrical filter element 20 and out to the engine through the opening at the lower center of the upper chamber 17.
Generally speaking, fuel tends to rise in the upper chamber 17 as the filter element 20 traps more and more contaminates from the bottom up. When the fuel level reaches the top of the filter element 20 in normal operation, this may be taken as a time to consider changing the filter element 20.
The present invention provides a vertical, two-part transparent housing having a fuel inlet for communicating fluid into the housing and a fluid outlet for communicating fluid downstream of said housing. A filter element is disposed within the housing between the fluid inlet and the fluid outlet for filtering the fluid. The housing includes a plastic top at least a portion of which is transparent for viewing the fluid level in the housing. A relief valve is mounted atop the filter element for maintaining and relieving a predetermined level of pressure across the filter element. A divider may connect to the filter element and extend between a housing wall and an unfiltered side of the filter element to divide the housing into an outer region and an inner region, wherein the outer and inner regions are in communication at a lower portion of the housing. A relief valve is in communication with a filtered side and the unfiltered side of the filter element and opens when the pressure across the filter element exceeds the predetermined pressure level thereby raising the level of fluid in the outer region of the housing. A segment of filter media may be adjacently mounted to the relief valve to filter any unfiltered fluid that passes through the relief valve to the filtered side of the filter element.
Alternatively, the relief valve may comprise a restrictive filter media integrally connected to the filter element. The restrictive filter media prevents the flow of fluid through the restrictive filter media until the pressure across the filter element reaches the predetermined pressure level thereby causing the fluid in the housing to rise.